Menz sheep breeding cooperative members review ram quality. Credit, CGIAR
Cross breeding is the process of breeding with the intention to create offspring that share the traits of both parent lineages or to produce an animal with hybrid vigour (the improved or increased function of any biological quality in a hybrid offspring).[1] In the developing world, cross breeding mainly seeks to improve the milk production of dairy cattle. Unlike milk production in developed countries where certain breeds of cows produce around 30 litres a day,[2] cows in some developing countries can only produce 1-2 litres per day.[3] Although productive capacity varies depending on the quality of feeding, nutrition and animal husbandry, much has to do with genetics.
Cattle in Kenya. Credit, S. MacMillan, ILRI
There are 2 dominant species of cattle in the world: the taurine cattle of the temperate climates of Europe, North Asia and West Africa and the zebu cattle of the hot arid and semi-arid regions of Africa and Asia. Although these species can naturally cross, today they are very different because of the selective breeding for increased milk production in taurine cows, which has led to the dominance of very high producing breeds such as the Holstein-Friesian.
Most smallholder farmers in Africa use indigenous livestock breeds, adapted to local conditions. For example, natural selection has produced zebu cattle with a high degree of heat tolerance. The zebu is also resistant to many tropical diseases and able to survive long periods of feed and water shortages. However, their dairy potential is poor as they yield low quantities of milk, mature late and usually do not let down milk unless simulated by the sucking of a calf.[4]
A holstein-friesian bull at the Kenya Animal Genetic Research Centre. Credit, P. Karaimu, ILRI.
Improving the productivity of indigenous breeds can be done with the introduction of foreign ones. In Zimbabwe and several countries in East Africa this has occurred with much success. For example, in Kenya improved dairy cattle account for 23% of the total cattle population and 75% of dairy cattle in eastern and southern Africa. Some countries, such as Uganda and Ethiopia, lag far behind; improved breeds only account for 3% and 1% respectively.[5]
Due to the low exchange of breeding animals and materials, as well as limited access and use of technologies such as artificial insemination, livestock populations remain mainly inbred.[6] High rates of inbreeding in Kenya, for example have also lead to reductions in dairy production from 6-7 litres per day down to just 3 litres.[7] Introducing breeding technologies such as cross breeding will be important for raising dairy productivity, but this will need to be met with support to enable farmers to manage this increased productivity. In many cases, extension services are already strained, but will be integral for smallholders to manage improved breeds.[8]
Contribution to Sustainable IntensificationCross breeding allows the improvement of standard production traits such as milk production, growth rate and production of total animal protein. Improved variety of cattle and other livestock can increase production efficiency and can reduce the amount of resources and inputs farmers require for livestock production. Higher levels of dairy production can in turn help smallholders respond to the growing demand for dairy products across Africa with the potential to improve incomes provided the necessary extension and marketing services and opportunities are accessible. Further, livestock are expected to be affected by climate change in several ways: feed and water limited by droughts, increasing heat stress and changes to disease prevalence.[9] Heat stress, for example, reduces production efficiency, lowers the animal’s welfare and is expected to result in significant loss due to death. Cross breeding can increase the resilience of the species to heat stress by reducing the amount of resources they require, thereby increasing the stability of livestock and farmers’ livelihoods.
One major advantage of crossbreeding is that it reduces levels of inbreeding, which often causes undesirable recessive disorders and a loss of genetic variation, as well as inbreeding depression (reduced biological fitness). Furthermore, crossbreeds benefit from “hybrid vigour” (also called heterosis), whereby traits such as fertility, health and longevity are particularly enhanced by crossbreeding. Other desirable traits such as milk or meat production can also be improved through this method, but these can be more unpredictable.
Crossbred livestock requires support from a number of improved management techniques, such as vaccination against local diseases, tick control or improved feed in order to achieve their genetic potential. Thus it requires training as well as inputs, to which smallholders and pastoralists may lack access, or for which they simply do not have the financial resources.[10] A study found that farmers with access to extension information generally kept crossbred goats, confirming that there is the possibility of increasing the genetic potential of local breeds through crossbreeding.[11]
The input costs for breeding – labour, feeds and vaccinations – are high, such that on-farm cross breeding may not offer any financial benefits to the farmers. Farmers also tend to prefer local breeds limiting adoption of improved breeds. Therefore it may be of greater benefit to integrate indigenous breeds into selection programmes to improve adoption rates of improved crossbreeds.[12] Community based cross-breeding may be one way to ensure that farmer and pastoralist preferences are taken into account.
Modern livestock breeding methods are often unsuitable for poor households with small flocks of sheep and goats, due to the technologies and costs involved and the skills required. Community-based breeding increases the productivity and profitability of indigenous breeds without undermining their resilience and genetic integrity, and without expensive interventions. Farmers are trained to improve selection methods – for example, retaining especially fast-growing ram lambs for breeding, rather than selling them young. Furthermore, the community flock is usually combined to create a large gene pool from which breeding rams can be selected. In many cases, a recording system to monitor the performance of individual animals is set up leading to continuous genetic improvement.[13]
